Merge #1333

1333: STM32: Adc V1 r=Dirbaio a=GrantM11235

Based on #947

Co-authored-by: Matthew W. Samsonoff <matt.samsonoff@gmail.com>
Co-authored-by: Grant Miller <GrantM11235@gmail.com>

examples/stm32f0/src/bin/adc.rs

@@ -0,0 +1,35 @@
+#![no_std]
+#![no_main]
+#![feature(type_alias_impl_trait)]
+
+use defmt::*;
+use embassy_executor::Spawner;
+use embassy_stm32::adc::{Adc, SampleTime};
+use embassy_time::{Delay, Duration, Timer};
+use {defmt_rtt as _, panic_probe as _};
+
+#[embassy_executor::main]
+async fn main(_spawner: Spawner) {
+    let p = embassy_stm32::init(Default::default());
+    info!("Hello World!");
+
+    let mut adc = Adc::new(p.ADC, &mut Delay);
+    adc.set_sample_time(SampleTime::Cycles71_5);
+    let mut pin = p.PA1;
+
+    let mut vrefint = adc.enable_vref(&mut Delay);
+    let vrefint_sample = adc.read_internal(&mut vrefint);
+    let convert_to_millivolts = |sample| {
+        // From https://www.st.com/resource/en/datasheet/stm32f031c6.pdf
+        // 6.3.4 Embedded reference voltage
+        const VREFINT_MV: u32 = 1230; // mV
+
+        (u32::from(sample) * VREFINT_MV / u32::from(vrefint_sample)) as u16
+    };
+
+    loop {
+        let v = adc.read(&mut pin);
+        info!("--> {} - {} mV", v, convert_to_millivolts(v));
+        Timer::after(Duration::from_millis(100)).await;
+    }
+}